The Minnesota Shear Test

The Minnesota Shear Test (MST) enables quick, simple, and quantitative determination of the wet or dry internal strength of the weakest plane of 0.25 inch (6.4 mm) and thicker wood fiber or particle panel products without gluing or clamping of the test specimen. It employs the principle that maximum shear stress develops at an angle 45 degrees to the direction of the force. Specimen orientation in MST is such that the face plane of the specimen is at 45 degrees to a compressive load applied at a uniform cross-head rate. A pivot point which transmits the force through the centroid of the specimen allows the testing of unevenly thick specimens, while a low friction device permits unrestrained lateral movement to occur as shear strain develops. Restraining bars and friction surfaces on the loading heads prevent slippage and transmit shear to the specimen. Slightly oversize, undersize, or out-of-square specimens can be tested. The results of this test can be used to accurately estimate internal bond or the values themselves can be used as an index of board quality.

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